An authentication error means a system could not establish the required identity using the information or method presented. Possible causes include incorrect credentials, wrong login format, account state or service-side handling. It is distinct from every later access-permission decision, and the exact wording should be recorded because applications can use broad messages for several conditions.
A practical example
A player expecting separate server, username and password fields may reject a complete playlist URL pasted into one field. Correcting the method and privately checking the issued details addresses that situation without changing the television's display or audio settings.
A common misunderstanding
Avoid repeatedly guessing credentials or publishing them in screenshots. Confirm the issued login method, exact message and relevant account status through the proper private support route before making broader changes.
Related terms
Stable technical definition. Editorial approach